EXPLORING NEW MASS REGIONS WITH THE ISOLTRAP SPECTROMETER

First direct mass measurements on rare earth isotopes around Gd-146 ha ve been performed with the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. More than 40 isotopes of the elements Pr, Nd, Pm, Sm, Eu, Dy and Ho have been measured with an accuracy of typically 1 x 10(-7) . In the case of Sm-141 isomeric and ground state (Delta E = 175 keV) were resolved. Since isobaric contaminations are present in the ISOLDE beam, these measurements on rare earth isotopes became only possible after the installation of a new cooler trap which acts an isobar separ ator.